1. Technical Field
This document relates to devices used during surgical procedures for treatment of heart conditions. For example, this document relates to extracorporeal circuit devices that can be used for on-pump open-heart surgery to facilitate surgical procedures such as coronary artery bypass grafting.
2. Background Information
Hollow fiber oxygenators are utilized within the extracorporeal circuit to meet a patient's gas exchange needs during cardiopulmonary bypass surgery. Blood from the patient is either gravity drained, or VAVD (vacuum assisted venous drainage) is used to obtain the required amount of flow to maintain sufficient volume in a reservoir. A centrifugal pump coupled with a magnetic driver is sometimes used in the main line of the circuit in order to pump blood from the reservoir, through the oxygenator, and finally back to the patient.
Prior to the initiation of bypass, a crystalloid priming solution is pumped through the extracorporeal circuit to remove air. The crystalloid priming solution remains in the extracorporeal circuit prior to the patient's blood being introduced. Hemodilution occurs when the blood mixes with the priming solution, thereby reducing the concentration of red blood cells (i.e., the hematocrit or hemoglobin value). Extracorporeal circuit devices with low prime volumes are preferable as they reduce the overall hemodilution. Any reduction in prime volume within the extracorporeal circuit can have an impact on hemodilution. If excessive hemodilution occurs such that the patient's hematocrit drops below a critical value (as specified by the physician and/or institution), a red blood cell transfusion may be deemed necessary. Studies have indicated that both low hematocrit values (possibly caused by hemodilution) and red blood cell transfusions correlate to higher patient mortalities.